Both Viola Davis and Michelle Obama have been in the spotlight lately, but for the most part, dark-skinned women are underrepresented in pop culture. We have plenty of hugely popular black singers and actresses — Beyoncé, Nicki Minaj, Halle Berry — but more often they are the light shades of tan. And the truth is,… »2/20/12 1:40pm 2/20/12 1:40pm